The concept of dental implants is well known in the art. Typically an inserted member (or members) provides the support for an artificial tooth as a replacement for a natural tooth or as an abutment for bridge work. This somewhat simplistic yet very straightforward approach to the implementation of a dental implant has, over the years, been subject to numerous modifications and improvements. Many of these modifications and improvements have been necessitated by unique situations resulting from the fact that not everyone's mouth or dental array is identical. Certain types of patients have peculiarities which cannot be accommodated by the standard dental implants typically available. For these individuals and others like them, efforts have been directed at providing specialized implants and methods of installing so as to handle these unique cases.
Additionally, over the years that dental implants have been used, dentists and oral surgeons have realized certain occurrences within the tissue and bone structure of the mouth which have lead to further developments that have improved the overall level of dental care by the use of implants. One type of dental implant wherein the supporting base and the post for the crown are of a one-piece construction is disclosed by the U.S. Pat. No. 3,950,850 issued to Driskell on Apr. 20, 1976. This single-piece approach was also followed in the design presented by U.S. Pat. No. 4,302,188 issued Nov. 24, 1981 to Driskell. In each of the foregoing patent references, a great deal of attention is directed to the design of the base and ways to improve the rigidity and strength of the base for anchoring and supporting the post which ultimately receives the crown or bridge work.
One area of concern which has evolved with the use of dental implants is the growth of bone and tissue around the implant after a socket has been prepared and the implant inserted in that socket. Clearly, it is an advantage to have the tissue and bone surrounding the socket initiate regrowth as quickly as possible and that it be compatible with the dental implant material.
With a one-piece implant, the typical procedure involves anchoring the implant in the prepared socket and thereafter securing the crown or bridge to the supporting post portion of the implant. Whatever the time requirement is for this surgical procedure, the patient leaves with the crown or temporarily splinted crown or bridge in place without "wearing" just the supporting post of the implant for a period of time while the socket heals and tissue and bone growth begins. Consequently, problems may be encountered by the patient if the crown or temporarily splinted crown or bridge and its supporting implant are jarred or struck or in some manner damaged prior to full seating and healing of the implant by the tissue and bone growth. One way to avoid this particular problem is to structure the dental implant into two members, an insertion member which goes into the prepared socket and a detachable and separable post portion which attaches to the inserted portion. By this two-part construction, it is possible to anchor the inserting portion of the implant in a subgingival manner into the socket and thereafter cover it with the flaps of the gum which have been cut away in order to initially prepare the socket. This covering by the gum tissue allows the socket to be protected and heal more quickly. After a time interval when healing has adequately occurred and both tissue and bone growth has been initiated in and around the anchoring portion of the implant so as to securely anchor it in place, the covering portion of the gum can be opened and thereafter the supporting post portion of the implant attached to the inserted portion. This two-piece post-type implant arrangement presents an advantage over the single-piece units due to the healing and tissue and bone growth migration which is permitted without the presence of a post or crown extending above the gum line which is susceptible to being hit, moved, or otherwise damaged to a degree that the inserted portion of the implant might be jarred within the socket and either cause injury or damage to the socket or otherwise weaken the bone and tissue grown which has already started.
This two-piece arrangement is often referred to as having a removable head and while numerous dental implants have been developed which feature such a removable head, the prior art of which the applicant is aware includes heads which are cemented, threaded or held in place with screw fasteners. Representative of this type of an approach is the Omnii implant system offered by Omnii International, 306 East Tyler Street, Tampa, Fla. The Omnii system includes three component parts, the first being an insertion member which is designed for insertion into a prepared socket. This first member includes an internally threaded head portion which is below or flush with the gum line when this member is fully inserted into the socket. The internally threaded open end of this member may be fitted with a plug and thereafter the plug may be removed and a crown support is threadedly installed. Apparently the purpose of the plus is to keep the internally threaded opening in the insertion member free from any debris or tissue migration such that once the plug is removed, the internally threaded opening is ready for receipt of the externally threaded stem portion of the implant post which then must be installed.
One of the problems with prior art devices such as that disclosed by the Omnii implant system literature is the alignment of the head portion with the root portion which has been inserted into the socket. As should be fairly well understood, the orientation of the inserted portion will determine the orientation of the crown support post due to the fact of its threaded engagement. Consequently, it becomes quite critical to precisely orient, radially, the inserted portion. Secondly, in the event the threaded engagement with the plug and the inserted portion becomes too tight or in any manner binds, the torque required to remove the plug will be transmitted to the inserted portion and weaken its anchoring within the bone and tissue which has begun to grow around the various contours of this inserted portion. For these reasons, it is felt that the type of device disclosed by the Omnii International publication entitled "Omnii Implant Systems" is really not as suitable as the present invention for an effective and reliable two-piece, post-type implant system.
The present invention, however, employs a locking taper concept where the head retention is dependent on the friction between the head and the root of the implant which is generated by impacting the female taper of the head with its male counterpart in the root portion. This method of attachment is believed to be preferred over the prior art devices, and alignment of the head portion with the root portion is easily made. Due to the conical nature of the tapered fit, the head portion which assembles to the inserted portion may be oriented in any manner desired at the time of making this assembly and is not in any way dependent on the orientation of the inserted portion.
By the use of a healing cap during the critical protected, unloaded healing phase, the present invention enables the root structure implant to securely anchor into its prepared socket. Further, the healing cap is dimensionally equivalent to the base or subgingival portion of the head. Its function in addition to isolating and protecting the healing root structure from trauma, is to form a new sulcus so that the implant head will fit perfectly when permanently placed 3-6 months later.
The present invention provides other advantages in that the present invention is specifically designed for patients with extensive edentulous areas, grafted areas, or other sites where adequate stabilization of the implant during the critical or early healing stage might be impractical or severely compromised. When the head and root structure of the present invention are assembled and lightly tapped together, they become in effect a single unit with the equivalent strength of a one-piece implant of the same dimensions.
A further advantage of the present invention not found in any of the prior art devices is the interchangeability of any size head either straight or angled with any size root structure and this permits adaptability of the present implants to sites with anatomical anomalies to a degree not previously possible. One example of the advantage of this flexibility would be in an upper lateral site where impinging adjacent roots may require the use of a root structure of minimal diameter while aesthetics would be improved with a head of, for example, 2 mm greater diameter. Another example of this advantage provided by the present invention would where a large diameter bridge abutment of substantial load-bearing abilities needed, but the requirements of the restoration suggest incorporation of a smaller diameter head. With the present invention, one has total flexibility using interchangeable standard components. The quick, precise surgical technique enabled by the present invention is unique and unobvious and not anticipated nor rendered obvious by any of the prior art relating to dental implants.